Diffusion transfer film units and their manufacture

ABSTRACT

DIFFUSION TRANSFER FILM UNITS WHEREIN PREDETERMINED LAYERS ARE TEMPORARILY LAMINATED TOGETHER ARE PREPARED USING A LAMINATING FLUID WHICH INCLUDES A REAGENT WHICH IMPROVES THE PHOTOGRAPHIC PERFORMANCE OF SAID FILEM UNIT OT THE STABILITY OF THE RESULTANT IMAGE. THE REAGENT MAY BE, E.G., AN ULTRAVIOLET LIGHT ABSORBER OR AN ANTIFOGGANT. IN A PARTICULARLY USEFUL EMBODIMENT, THE REAGENT IS A REAGENT WHICH WILL SUPPRESS TRIBOLUMINESCENCE.

United States Patent 3,806,346 DIFFUSION TRANSFER FILM UNITS AND THEIR MANUFACTURE Stanley M. Bloom, Waban, and Howard G. Rogers, Weston, Mass., assignors to Polaroid Corporation, Cambridge, Mass. No Drawing. Filed Apr. 24, 1972, Ser. No. 246,743 Int. Cl. G03c 1/48 U.S. CI. 96-76 R 30 Claims ABSTRACT OF THE DISCLOSURE Diffusion transfer film units wherein predetermined layers are temporarily laminated together are prepared using a laminating fluid which includes a reagent which improves the photographic performance of said film unit or the stability of the resultant image. The reagent may be, e.g., an ultraviolet light absorber or an antifoggant. In a particularly useful embodiment, the reagent is a reagent which will suppress triboluminescence.

This application relates to photography and, more particularly, to diffusion transfer photography and film units for use therein.

A number of diffusion transfer photographic processes have been proposed wherein the resulting photograph comprises the developed silver halide emulsions retained with the dye-image carrying layer as part of a permanent laminate. The image-carrying layer is separated from the developed silver halide emulsions in said laminate by a light-reflecting layer, preferably a layer containing titanium dioxide. Illustrative of patents describing such products and processes are US. Pat. No. 2,983,606 issued Mar. 9, 1961 to Howard G. Rogers, US. Pat. Nos. 3,415,- 644, 3,415,645 and 3,415,646 issued Dec. 10, 1968 to Edwin H. Land, US. Pat. Nos. 3,594,164 and 3,594,165 issued July 20, 1971 to Howard G. Rogers, and US. Pat. No. 3,647,347 issued Mar. 7, 1972 to Edwin H. Land.

Referring more specifically to the aforementioned US. Pat. No. 3,415,644, said patent discloses photographic products and processes employing dye developers wherein a photosensitive element and an image-receiving layer are maintained in fixed relationship prior to photoexposure and this fixed relationship is maintained after processing and image formation to provide a laminate including the processed silver halide emulsions and the image-receiving layer. Photoexposure is made through a transparent (support) element and application of a processing composition provides a layer of light-reflecting material to provide a white background for viewing the image and to mask the developed silver halide emulsions. The desired color transfer image is viewed through said transparent support against said white background.

While film units of the foregoing type basically comprise two separate sheet-like elements, a number of advantages can be realized by laminating the two elements during the manufacture and assembly process and delaminating the elements following exposure by and in response to spreading of the processing liquid. For example, a prelaminated integral film unit is easier to handle and manipulate during assembly and during exposure and processing within the camera; it is more compact and hence, permits smaller and less bulky film packs and cameras; and it is less subject to buckling and distortion due to temperature and humidity changes and more likely to lie flat and remain planar during exposure. Since the elements are in contact throughout the entire extent of their facing surface, every portion of each element is exposed to substantially the same ambient conditions so that each portion has the same physical and chemical properties as every other portion and the elements produce uniform 3,806,346 Patented Apr. 23, 1974 results, the photographically active layers of the film unit are not only protected against mechanical damage, but are additionally protected against changes in ambient conditions which may also effect their function. Moreover, processing, specifically, spreading of the processing liquid within the film unit, is facilitated since there is little or substantially no air between the sheets to interfere with liquid distribution.

Methods of laminating said elements have been described in US. 'Pat. 3,652,281 to Albert 1.. Bachelder and Frederick C. Binda and US. Pat. No. 3,652,282 to Edwin H. Land, both issued Mar. 28, 1972. A particularly useful and preferred laminating process utilizes a watersoluble polyethylene glycol and is described and claimed in the copending application of Edwin H. Land, Ser. No. 247,023, filed concurrently herewith as a continuationin-part of application Ser. No. 209,754 filed Dec. 20, 1971.

The present invention is concerned with providing prelaminated integral film units having improved properties and with providing laminating processes of increased versatility.

A primary object of this invention is to provide integral negative-positive diffusion transfer film units and processes of forming said film units by laminating two sheet-like elements, wherein the laminating composition is used to provide a reagent useful in said diffusion transfer process, such as an ultraviolet absorber or an antifoggant.

A further object of this invention is to provide integral negative-positive diffusion transfer film units which include a reagent adapted to suppress triboluminescence.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the product possessing the features, properties and relation of components and the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description of the invention.

The present invention is applicable to a wide variety of color diffusion transfer processes and the arrangement and order of the individual layers of the film used to such color processes may vary in many ways as is known in the art, provided the final image is an integral negativepositive reflection print as described above. For convenience, however, the more specific description of the invention may be by use of dye developer diffusion transfer color processes and of integral negative-positive film units of the type contemplated in the previously mentioned US. Pat. No. 3,415,644.

In the manufacturing and assembling of a film unit according to this invention, the photosensitive and second or image-receiving elements are laminated to one another as a step which is performed early in the assembly process. For example, photosensitive and second elements such as described in the foregoing above-cited patents, are manufactured by coating the appropriate layers on elongated support strips by conventional continuous coating practices, including baking the coated strips to form 1ntegral, finished laminates that can be handled and/or utilized (without change) as photosensitive and second or image-receiving elements. A laminating solution, preferably including a water-soluble film-forming polymer, is distributed as a laminating solution between the sheets to effect the lamination thereof and to insure delamination by the processing liquid at the desired layers. An adhesive bond may thus be provided by a mass production method, which bond is of predetermined strength and does not vary substantially with time or as a result of changes in humidity or temperature. The components of the laminating solution must be inert or at least compatible with all of the materials of the film unit; it should form a solid laminating layer; and it should not blush or otherwise interfere with the optical properties of the laminate.

A laminating solution particularly suited for laminating a gelatin topcoat (a water-soluble polymer) of a photosensitive element to a polyvinyl alcohol topcoat (also a water-soluble polymer) of an image-receiving element or to an aqueous processing solution soluble or permeable coating on a second element employed primarily in spreading the processing liquid, comprises 5 parts of water to 1 part (by weight) of polyethylene glycol having a molecular weight range of about 6000 to 7500 and commercially available from Union Carbide Corporation under the trade name Carbowax 6000. It has been found that suitable bonds may be obtained between gelatin and polyvinyl alcohol containing layers by distributing approximately 80 to 200 mg./ft. of the above solution between said layers as they were brought into face-to-face, laminating relationship e.g., at the nip of a pair of pressure-applying rollers.

The quantity of polyethylene glycol coated per square foot will depend in part upon the molecular weight of the polyethylene glycol used and in part upon the bond strength desired. Other factors determinative of both the quantity of polyethylene glycol coated per square foot as well as the bond strength include the speed of sheet movement relative to solution flow rate to the nip, the pressure applied by the rollers to achieve lamination and the solution concentration. These factors may be readily determined by simple routine tests utilizing the polymers being bonded to produce a stable bond which does not grow stronger or weaker with changes in ambient conditions. For example, it has been found that the bond strength is increased by reducing the quantity of polyethylene glycol while an increase in the amount of polyethylene glycol will reduce the bond strength. Polyethylene glycol has been found to be unique and especially useful in that it not only controls the bond strength within narrow limits, but that it is a stable, hydroscopic solid material which insures constant bond strength despite changes in temperature and humidity which would ordinarily alter, e.g., strengthen, a direct bond between two water-soluble, polymeric layers. Polyethylene glycol having a molecular weight in excess of 6000 is preferred because it is a solid at ordinary temperatures, whereas lower molecular weight polyethylene glycol tends to be less solid and more fluid. An advantage of the solid form of polyethylene glycol is that the adherence between the elements is almost immediate and is sufficient to permit the handling and manipulation of the laminated sheets associated with further assembly steps in the formation of the film unit, thus eliminating delays required for drying and bond strengthemng.

By way of example, the coated photosensitive element and the second or image-receiving element can be laminated or bonded to one another by advancing the elements (or elongated strips) between a pair of pressure-applying rolls while introducing an aqueous solution of polyethylene glycol laminating agent between the elements at the nip of the rolls. Thus, the photosensitive and second or imagereceiving sheets are advanced into superposition at the nip of a pair of laminating rolls, one of which may be provided with flanges at its ends for containing the laminating liquid which is introduced between the sheets at the nip of the rolls through a tube where the liquid is permitted to form a meniscus. The liquid is distributed in contact with the sheets and the sheets are pressed together so as to adhere them to one another over substantially their entire facing surfaces.

The remaining steps in the manufacture and assembly process illustrated may include advancing the laminated sheets from laminating rolls into and through an oven where they are baked to evaporate the solvent of the laminating liquid and thence to cutting means where the individual sandwiches are cut to length and thereafter submitted to the remaining assembly steps. An advantage of employing polyethylene glycol as described is that the two sheets need not be heated following lamination but may be subjected immediately to the manipulation and handling involved in assembling the film units according to processes disclosed, for example, in US. patent applications, Ser. Nos. 135,539, filed Apr. 20, 1971; 140,537, filed May 4, 1971; and 102,447, filed Dec. 29, 1970 (now US. Pat. No. 3,694,206 issued Sept. 26, 1972); in which the laminate is severed into individual film unit-sized sections at a latter stage in the assembly process.

For further details of processes for laminating and assembling integral negative-positive film units, reference should be made to the above-noted United States patents and applications.

In accordance with the present invention, the laminating solution includes at least one reagent whose function is not to bond or aid in bonding together a predetermined pair of layers within the laminated film unit. This reagent may serve a function in the development of the exposed photosensitive material, e.g., an antifoggant. Alternatively, the reagent may be one which helps to stabilize or otherwise improve the properties of the resulting transfer image, e.g., an ultraviolet light absorber. In yet another and particularly useful embodiment, the reagent is one which is adapted to suppress triboluminescence.

The reagent incorporated by means of the laminating solution may be either soluble or insoluble therein, diffusible or non-ditfusible from the stratum formed by the laminating solution, and either soluble or insoluble in the processing composition, according to the requirements of the particular film unit and transfer process. The laminating solution advantageously may be used to provide a reagent which is unstable for prolonged periods in alkaline solution but which preferably is excluded from one or more layers of the film unit until an alkaline processing composition is applied; if such a reagent is waterinsoluble, it will remain essentially between the thus bonded layers until dissolved by an alkaline processing composition used to delaminate and perform the diffusion transfer process.

As noted above, an important aspect of this invention is the provision in an integral negative-positive film unit of a reagent adapted to suppress triboluminescence. Triboluminescence is luminescence or light resulting from an electrical discharge, an electrical charge having been generated by frictional forces. In integral negative-positive film units wherein the requisite layers are laminated together prior to exposure, the processing composition may be distributed between a predetermined pair of layers within said laminate if the strength of the bond between said predetermined pair of layers is weaker than that of the bonds between other pairs of layers. In practice, a processing fluid is ejected from a rupturable container so positioned as to insure that the processing fluid is forced between the predetermined layers. These layers tend to delaminate ahead of the wave front of processing fluid. This delamination has been discovered to be capable of generating triboluminescence of an intensity suflicient to visibly decrease the maximum density of the resulting transfer image. Indeed, the triboluminescence has been observed as blue light when such a prelaminated integral negative-positive film unit was processed in a photographic darkroom. This visual observation was confirmed by processing unexposed, prelaminated film units in the dark and measuring the red, blue and green reflection densities of the resulting black spread. (The term black spread is sometimes used to describe the black transfer image obtainable by diffusion transfer processing of an unexposed photosensitive element. Since there has been no photoexposure, the transfer image should be black, as the individual image dyes should transfer in unreduced density, unless development is caused by sources of developable silver halide other than photoexposure). In one such test, pairs of a multicolor photosensitive element and an image-receiving element were laminated together using as the laminating fluid a solution of 150 g. of Carbowax 6000 (trade name of Union Carbide Corporation for a polyethylene glycol having an average molecular weight of approximately 6000) in 750 cc. of water at a coverage of 125 mg./ft. of said solution. After drying, one such integral negative-positive film unit (herein referred to as film unit A) was delaminated manually (in the dark) prior to distributing the processing composition between the image-receiving layer and the blue-sensitive silver halide emulsion layer. A second such laminated integral negative-positive film unit (herein referred to as film unit B) was processed by allowing the processing fluid to cause the delamination. The reflection densities of the respective integral negative-positive reflection print black spreads so obtained were:

Film unit Red Green Blue This test demonstrates that the triboluminescence is of an intensity sufficient to cause the loss of 0.4 unit of blue reflection density. This test also confirms that the observed loss in blue density was not due to the presence of the polyethylene glycol, since it was present in both film units.

A prelaminated integral negative-positive film unit (herein referred to as film unit C) was prepared using the above described laminating fluid to which had been added 2.0 g. of the ammonium salt of perfluorooctanoic acid, i.e.,

H-CIIFHCOONHQ:

Film unit Red Green Blue This test clearly demonstrates the ability of the perfluorooctanoic acid to suppress triboluminescence and maintain blue density. As will be readily apparent to those skilled in the art, the eificacy and compatibility of other reagents adapted to suppress triboluminescence may be readily determined by routine testing.

The reduction in blue reflection density observed in the above test was essentially uniform across the image area. It is thus apparent that the observed phenomenon is different from the lightning streaks" sometimes observed in photographic films as a result of static electricity. Indeed, the uniformness of the observed loss of density actually obscured the source of the problem and led to false starts to solve the problem on the hypothesis that one of the chemicals present was causing fogging of the blue-sensitive silver halide.

Since certain changes may be made in the above product and method without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A photographic film unit adapted to be exposed and processed to produce a diffusion transfer image comprising, in combination:

a laminate including, as essential layers and components thereof, two dimensionally stable layers at least one of which is transparent and intermediate said dimensionally stable layers, a plurality of layers including at least an image-receiving layer and at least one photosensitive silver halide layer; and

a rupturable container of a processing composition coupled to said dimensionally stable layers in position to discharge its liquid contents for spreading between a predetermined pair of layers of said laminate and thereby causing delamination of said laminate between said predetermined layers thereof;

said laminate including in a layer thereof a reagent adapted to suppress triboluminescence when said delamination is effected by spreading of said processing composition.

2. A photographic film unit as defined in claim 1 wherein said laminate includes a plurality of layers including a photosensitive layer containing a plurality of strata comprising selectively sensitive silver halide emulsions each having associated therewith a diffusion transfer process image dye-providing material; and an image-receiving layer adapted to receive image dyes provided by said image dye-providing materials.

3. A photographic film unit as defined in claim 2 wherein said laminate includes a red-sensitive silver halide layer having associated therewith a cyan image dye-providing material, a green-sensitive silver halide layer having associated therewith a magenta image dye-providing material, and a blue-sensitive silver halide layer having associated therewith a yellow image dye-providing material.

4. A photographic film unit as defined in claim 2 wherein said laminate includes a red-sensitive silver halide layer having associated therewith a cyan dye developer, a green-sensitive silver halide layer having associated therewith a magenta dye developer, and a blue-sensitive silver halide layer having associated therewith a yellow dye developer.

5. A photographic film unit as defined in claim 3 wherein said rupturable container is so positioned as to distribute its contents between said blue-sensitive silver halide and said image-receiving layer.

6. A photographic film unit as defined in claim 3 wherein said rupturable container is so positioned as to distribute its contents between said blue-sensitive silver halide layer and said dimensionally stable layer closest to said bluesensitive silver halide layer.

7. A photographic film unit as defined in claim 1 wherein said predetermined layers are temporarily bonded to each other by a stratum including a water-soluble polymer.

8. A photographic film unit as defined in claim 7 wherein said water-soluble polymer is a polyethylene glycol.

9. A photographic film unit as defined in claim 8 wherein said polyethylene glycol has a molecular weight of about 6000 to 7500.

10. A photographic film unit as defined in claim 7 wherein said stratum of water-soluble polymer includes a reagent adapted to suppress triboluminescence.

11. A photographic film unit as defined in claim 10 wherein said reagent is the ammonium salt of perfluorooctanoic acid.

12. In a method of forming a diffusion transfer photographic film unit, said film unit comprising a plurality of layers forming a laminate including two outer dimensionally stable supports at least one of which is transparent, said plurality of layers including an image-receiving layer and at least one photosensitive silver halide layer, said laminte including a pair of layers bonded to each other with a bond strength less than the bond between any other layers of said laminate, said method including the step of bringing said supports together with one of said predetermined layers on each of said supports, said predetermined layers being in face-to-face relationship with a laminating fluid therebetween, and drying the resulting laminate, the improvement wherein said laminating fluid includes a reagent which is an ultraviolet light absober, an antifoggant or a reagent adapted to sup press triboluminescence.

13. The method defined in claim 12 wherein said reagent is an ultraviolet absorber.

14. The method as defined in claim 12 wherein said reagent is a reagent adapted to suppress triboluminescence.

15. The method as defined in claim 12 wherein said reagent is an antifoggant.

16. The method as defined in claim 12 wherein said laminating fluid is distributed between said image-receiving layer and said silver halide layer.

17. The method as defined in claim 11 wherein said laminating fluid comprises a solution of a water soluble polymer.

18. A photographic film unit adapted to be exposed and processed to produce a difiusion transfer image comprising, in combination:

a laminate including, as essential layers and components thereof, two dimensionally stable layers at least one of which is transparent and intermediate said dimensionally stable layers, a plurality of layers including at least an image-receiving layer and at least one photosensitive silver halide layer; and

a rupturable container of processing composition coupled to said dimensionally stable layers in position to discharge its liquid contents for spreading between a predetermined pair of layers of said laminate and thereby causing delamination of said laminate between said predetermined layers thereof;

said laminate including said predetermined pair of layers being temporarily bonded to each other by a stratum including a water-soluble polymer, said stratum also including a reagent adapted to suppress triboluminescence when said delamination is effected by spreading of said processing composition.

19. A photographic film unit as defined in claim 18 wherein said laminate includes a plurality of layers including a photosensitive layer containing a plurality of strata comprising selectively sensitive silver halide emulsions each having associated therewith a diffusion transfer process image dye-providing material; and an image-receiving layer adapted to receive image dyes provided by said image dye-providing materials.

20. A photographic film unit as defined in claim 18 wherein said laminate includes a red-sensitive silver halide layer having associated therewith a cyan dye developer,

a green-sensitive silver halide layer having associated therewith a magenta dye developer, and a bluesensitive silver halide layer having associated therewith a yellow dye developer.

'21. A photographic film unit as defined in claim 20 wherein said water-soluble polymer is a polyethylene 1 col. 22. A photographic film unit as defined in claim 18 wherein said water-soluble polymer is a polyethylene glycol and said reagent is the ammonium salt of perfluorooctanoic acid.

23. A photographic film unit adapted to be exposed and processed to produce a diffusion transfer image comprising, in combination:

a laminate including, as essential layers and components thereof, two dimensionally stable layers at least one of which is transparent and intermediate said dimensionally stable layers, a plurality of layers in cluding at least an image-receiving layer and at least one photosensitive silver halide layer; and

a rupturable container of processing composition coupled to said dimensionally stable layers in position to discharge its liquid contents for spreading between a predetermined pair of layers of said laminate and thereby causing delamination of said laminate between said predetermined layers thereof; said laminate including said predetermined pair of layers being temporarily bonded to each other by a stratum including a water-soluble polymer, said stratum also including an ultraviolet light absorber.

24. A photographic film unit as defined in claim 23 wherein said laminate includes a plurality of layers in cluding a photosensitive layer containing a plurality of strata comprising selectively sensitive silver halide emulsions each having associated therewith a diflusion transfer process image dye-providing material; and an image-receiving layer adapted to receive image dyes provided by said image dye-providing materials.

25. A photographic tfilm unit as defined in claim 24 wherein said laminate includes a red-sensitive silver halide layer having associated therewith a cyan dye developer, a green-sensitive silver halide layer having associated therewith a magneta dye developer, and a blue-sensitive silver halide layer having associated therewith a yellow dye developer.

26. A photographic film unit as defined in claim 25 wherein said water-soluble polymer is polyethylene glycol.

27. A photographic film unit adapted to be exposed and processed to produce a diifusion transfer image comprising, in combination:

a laminate including, as essential layers and components thereof, two dimensionally stable layers at least one of which is transparent and intermediate said dimensionally stable layers, a plurality of layers including at least an image-receiving layer and at least one photosensitive silver halide layer; and

a rupturable container of processing composition coupled to said dimensionally stable layers in posi tion to discharge its liquid contents for spreading between a predetermined pair of layers of said laminate and thereby causing delamination of said laminate between said predetermined layers thereof;

said laminate including said predetermined pair of layers being temporarily bonded to each other by a stratum including a water-soluble polymer, said stratum also including an anti-foggant.

28. A photographic film unit as defined in claim 27 wherein said laminate includes a plurality of layers including a photosensitive layer containing a plurality of strata comprising selectively sensitive silver halide emulsions each having associated therewith a diffusion transfer process image dye-providing material; and an imagereceived layer adapted to receive image dyes provided by said image dye-providing materials.

29. A photographic film unit as defined in claim 28 wherein said laminate includes a red-sensitive silver halide layer having associated therewith a cyan dye developer, a green-sensitive silver halide layer having associated therewith a magenta dye developer, and a blue-sensitive silver halide layer having associated therewith a yellow dye developer.

30. A photographic film unit as defined in claim 29 wherein said water-soluble polymer is a polyethylene glycol.

References Cited UNITED STATES PATENTS 3,415,644 12/1968 Land 96-29 D 3,552,972 1/1971 Meyer 96-87 A 3,325,283 6/1967 Barstow 9676 R FOREIGN PATENTS 2,025,688 11/1970 France.

I. TRAVIS BROWN, Primary Examiner J. L. GOODROW, Assistant Examiner Us. 01. X.R. 96-87A 

